The present invention relates to the field of semiconductor device structures, and more in particular to optoelectrical or optoelectronic devices. More precisely the present invention is related to a socket, and to a system for optoelectronic interconnection. The present invention is also related to a method of fabricating such sockets and such systems.
The increased integration of transistors on single chips made possible by the submicron CMOS technology raises the problem of speed and performance limitation of electronic systems through the interconnect structures between chips or with other structures. A possible solution to this problem of CMOS interconnect bottlenecks could be the use of optical links or interconnects between chips. In a number of applications, especially to achieve high density interconnects, optical interconnects are advantageous over electrical interconnects. For instance, optical interconnects can reach a higher interconnect density and lower power consumption than electrical interconnects.
In order to achieve high density optical interconnects, it is necessary to realize high density arrays of light sources and light detectors, and furthermore to use an optical path or channel between sources and detectors which sustains a high density of optical channels. The light sources used to send the optical signals through the optical interconnect channels receive their input and possibly at least part of their power from electrical signals. These electrical signals can originate from an integrated circuit, or from a board. Furthermore, at the other end of the optical interconnect channel are detectors, which also require electrical power to operate, and which convert the received optical signals into electrical signals. Hence, it is clear that high density optical interconnects require a high density of electrical or optical devices to possibly deliver at least part of the required electrical power to run the optical interconnect, as well as to send and retrieve the signals.
Obviously, the foregoing analysis can be applied as well to interconnect systems that make use of another form of electromagnetic radiation than light.
In many optical applications, it is required to have a transparent substrate for an optoelectronic device such as a light-emitting device, a photodetector, a modulator or a CCD sensor. An application example is when an optoelectronic device is contacted from the front side by flip-chip mounting, while the light has to be transported through the substrate. Many substrates are poorly or not transparent for the light emitted or detected in the active semiconductor layers grown on them. For example, Gallium-Arsenide (GaAs) or Aluminium-Gallium-Arsenide (AlGaAs) or InGaP or InAlGaP active layers emit and detect light with a peak wavelength that is strongly absorbed by the GaAs substrate on which they are typically grown. Hence, light-emission or light-detection through the original substrate is not possible. A possible solution to this problem is to remove the original substrate in a process such as described in U.S. Pat. No. 5,578,162. Another possible solution is to replace the original substrate by a transparent substrate, such as a glass plate.
U.S. Pat. No. 5,093,879 discloses an optoelectrical connector for accommodating high density applications. This patent specification however does not disclose and does not enable to fabricate integration neither alignment of a connection for the electrical signals to the devices for emitting and/or detecting electromagnetic radiation, wherein the functioning of said devices is being controlled by said electrical signals.
U.S. Pat. No. 5,625,811 discloses an optically interconnected multichip module. The patent shows a dense integration of thin layers of semiconductor material with devices (chips) integrated therein and which are bonded to a fiber optic face plate. These chips are integrated in a multichip module and the fiber optic face plate is providing the optical intraconnection or optical transmission medium between the chips. The optical intraconnection (waveguide) is not flexible and does not allow for communication between chips which are in the same plane or in a remote location. This patent does not address the problem of a connector to an external apparatus or external devices that is versatile in use and easy to use.
The use of fiber optic face plates in combination with optoelectrical devices has further been proposed, e.g. in U.S. Pat. No. 5,074,683, and in U.S. Pat. No. 5,652,811, and in U.S. Pat. No. 5,578,162.
U.S. Pat. No. 5,631,988 discloses an optical interconnect that couples multiple optical fibers to an array of optoelectrical devices. The connector comprises a holder, a plurality of optical fibers attached to the holder, and guiding means. This connector is quite elaborate and not compact in providing the optical path of the interconnection signals. Moreover, the direct contact of the optical fiber bundles to the optoelectrical devices can degrade such devices, in particular because the optical connection is detachable.
U.S. Pat. No. 5,367,593 provides an optical/electrical connector that includes a molded base with alignment guides and with a well for integrating an electronic circuit. Also this device is not compact and provides an optical interconnection path only for a 1-dimensional array. The teaching of this patent does not disclose nor does it suggest an optoelectrical interconnect in a dense and compact configuration which is flexible in use for a multitude of configurations such as 2-dimensional arrays of light-emitting devices on an electronic circuit.
It is an object of the present invention to disclose a socket that is easy in use for optical or optoelectronic or optoelectrical interconnection. The socket of the invention provides an interconnection device that has a dense, compact configuration. In an embodiment of the invention, the socket of the invention can be handled as a stand-alone package that allows the interconnection between electrical signals and an external apparatus for transmitting the optical signals, preferably via a high density of optical channels. The socket of the invention allows for a flexible communication between devices being controlled by electrical signals such as integrated circuits. With the socket of the invention a communication between chips in an in-plane configuration or in any other configuration or dimension is feasible. A communication between chips in an in-plane configuration (a 2-dimensional array of chips) or in any other configuration or dimension (for instance a 1-dimensional or 3-dimensional array) is feasible.
It is another object of the present invention to provide a socket for optoelectrical interconnection with a transparent substrate for high-density optical input/output applications in which the electrical input/outputs are connected to the optical input/outputs. But the electrical input/outputs are at another side of the socket, preferably opposite, to the optical input/outputs.
It is a further object of the invention to disclose a socket with features and markers for attachment and alignment of optical transfer media such as optical fibers, optical fiber bundles and optical imaging fiber bundles. The alignment features and markers allow to align the optical transfer media to the connection for electrical signals. The markers can be integrated in or can be provided on a fiber optic face plate substrate forming part of the socket. The alignment features and markers in an embodiment of the invention can comprise magnetic means for alignment and/or attachment. The optical fibers, fiber bundles or imaging fiber bundles can then further be aligned and attached to detectors integrated in a silicon integrated circuit.
Thus, here is provided a socket for optoelectrical interconnection, comprising a connection for electrical signals; an array of devices emitting and/or detecting electromagnetic radiation, the functioning of said devices being controlled by said electrical signals; and a connection to an external apparatus, the connection including a transmitter or a channel for said radiation. Said connection for electrical signals can be connected with at least a part of said devices of said array. Said connection for electrical signals can be aligned through at least one marker in or on said connection to said external apparatus with at least a part of said devices of said array. The marker can be aligned with at least part of said devices of said array. Said external apparatus can include a channel or a high density of channels for said electromagnetic radiation. The external apparatus can also include a detector and/or devices for emitting electromagnetic radiation. Said connection for electronic signals can be at a first side of said socket and said connection to said external apparatus can be at a second side of said socket.
The socket of the invention can be configured as an interconnection device for optoelectrical interconnection, comprising a connection for electrical signals; an array of devices emitting and/or detecting electromagnetic radiation, the functioning of at least a part of said devices being controlled by said electrical signals; and connection to an external apparatus including a transmitter for said radiation, said connection to said external apparatus comprising a substrate with a plurality of light channels for said radiation. The connection can be such that essentially each device of said array is aligned with at least a subset of said light channels. In an embodiment of the invention, said substrate can be a fiber optic face plate. According to this embodiment of the invention, the different parts of the interconnection device or socket are brought together adjacent one to another in a dense, compact configuration. The different parts can however be spatially separated. According to a preferred embodiment, such dense configuration can be achieved with having the different parts of the socket integrated on a substrate such as a PCB-board with a mounting technique, such as a flip-chip technique for mounting the parts, providing the alignment of the different parts one to another.
In an advantageous embodiment of the invention, the fiber optic face plate can include microlenses. The microlenses can be made according to the teaching of U.S. Pat. No. 5,871,888 or of any patent or reference cited within or with respect to this patent, U.S. Pat. No. 5,871,888 or any of the prior art teachings being incorporated herein by reference.
The socket of the invention can also be configured as an integrated socket providing the socket of the invention in a compact, single interconnection device with each of the different parts of the socket is abutting at least one of the other parts of the socket.
The socket of the invention can also have at least one marker in said connection to said external apparatus, said marker being aligned with at least part of said devices of said array.
In a preferred embodiment of the invention, in the socket essentially each of said devices for emitting and/or detecting electromagnetic radiation of said array is being confined through form and functioning and essentially each of said devices for emitting and/or detecting electromagnetic radiation of said array is being aligned with at least a part of said connection for electronic signals. With the term confined through form and functioning it is meant that without additional means or without additional structural features such as extended, large isolation features in the array of devices, each of said devices can be addressed individually via the connection for electrical signals. Such confinement through form and functioning can be done e.g. when said devices are being integrated in a single thin film semiconductor. The term confined through form and functioning is also used more generally in this specification. For instance, in an embodiment of the invention, said connection for electronic signals can include an electrically conducting glue providing separate conduction paths. These paths can be confined through form and functioning which means that without additional means the glue is providing a separate conduction path to substantially each of the devices. Also detector devices can be used that are confined through form and functioning.
In an embodiment of the invention, one can also use devices that can both emit and detect electromagnetic radiation. Examples of such devices are optical thyristors or p-n diodes.
In a preferred embodiment of the present invention, said socket includes a thin-film semiconductor layer attached to a transparent fiber optic face plate substrate, such that optoelectrical devices processed in the thin film semiconductor layer are electrically contacted from the side opposite to the side of the face-plate attachment. Markers and marker features for alignment are made in or on the fiber optic face plate. In an aspect of the invention, two sockets are abutted one against the other and information is transmitted between the light emitters/detectors of the respective sockets. An example of such use is the information transmission to and from a board with electronic devices to a rack including a multiple of such boards.
Still a further object of the invention is to disclose a system for transmitting information comprising at least one channel for electromagnetic radiation; a socket for optoelectronic interconnection, and said channel comprising a channel marker, said channel marker being aligned with a socket marker. The socket includes a connection for electronic signals; an array of devices emitting and/or detecting electromagnetic radiation, the functioning of said devices being controlled by said electronic signals, said connection being connected and aligned with at least a part of said devices of said array; a connection for said channel for said radiation; and at least one socket marker in said connection for said channel, said marker being aligned with at least part of said devices of said array. The system can further comprise an array of devices emitting and/or detecting electromagnetic radiation, said array of devices being connected to said channel, the detectors of said array being adapted for receiving said radiation and converting said radiation into electronic signals. Said detectors can further comprise detector markers such that said channel is aligned with said detector markers and such that specific parts of said array of radiation emitting devices are aligned with specific parts of said detector.
Yet another object of the invention is to disclose a method of fabricating an optoelectrical structure wherein the optical devices forming part of the structure are controlled by electrical connections that can be aligned with an external channel for transmitting the optical information. The method of fabricating the optoelectrical structure provides a way of aligning the different parts of the optoelectrical structure one with respect to the other.
In an embodiment of this object of the invention, a method of large-scale and wafer-scale fabrication of arrays of optoelectronic devices with above-mentioned transparent fiber optic face plate substrate is disclosed. A preferred embodiment of the invention reveals wafer scale fabrication of the optoelectronic devices on a fiber optic face plate including integrated socket features.
Yet any combination can be made of any of the embodiments of the devices or methods of the invention, disclosed in the present patent application.